There have been forklifts provided with a hydraulic driving device called a hydro static transmission device (HST) between an engine as a driving source and driving wheels (for example, see Patent Literature 1). The hydraulic driving device is equipped with a variable displacement traveling hydraulic pump driven by the engine and a variable displacement hydraulic motor driven by hydraulic oil discharged from the traveling hydraulic pump in a main hydraulic circuit as a closed circuit, and allows a vehicle to travel by transmitting the drive of the hydraulic motor to the driving wheels.